4x−54−5x\frac{4 x-5}{4-5 x}4−5x4x−5
4x+55x−4\frac{4 x+5}{5 x-4}5x−44x+5
4x+54−5x\frac{4 x+5}{4-5 x}4−5x4x+5
5x+44−5x\frac{5 x+4}{4-5 x}4−5x5x+4